The present invention relates generally to a reinforced structural member for use in strengthening the stiffness and strength of different portions of an automotive vehicle. More particularly, the present invention relates to a structural reinforcement system for use in an automotive pillar, especially an automotive xe2x80x9cBxe2x80x9d pillar, which serves to absorb energy in the vehicle body and pillar structure in the event of an front offset impact to the automotive vehicle through the use of a reinforced member coated over a portion of its surface with an expandable material, the combination of which may be employed to increase the structural stiffness and strength of the automotive vehicle.
For many years the transportation industry has been concerned with designing reinforced structural members that do not add significantly to the weight of a vehicle. For example, U.S. Pat. Nos. 5,755,486; 4,901,500; and 4,751,249 describe prior art reinforcing devices. While these prior art devices may be advantageous in some circumstances, there is needed a simple low cost structure or system that permits coupling the reinforcement member to a variety of structures of varying geometric configurations. Further, changing developments in both consumer demand and automotive manufacturing processes are continually creating new and different types of vehicles and vehicle segments for the consumer market. Many of these new vehicle designs, such as crew/club cab trucks, car/truck hybrid vehicles, and cars having xe2x80x9cthirdxe2x80x9d doors for example present a number of unique applications and challenges to provide structural reinforcement systems that strengthen the desired section of an automotive vehicle, while still providing sound and vibration characteristics, all in a manner which can be streamlined into the automotive vehicle manufacturer""s production process in a cost efficient manner.
In the automotive industry, there is also a need for a relatively low cost system for reinforcing automotive pillar structures in a vehicle, which can serve to absorb energy in a front offset impact to the vehicle, by reinforcing the pillar to redirect pillar travel in an impact.
The present invention is directed to a structural reinforcement system and, more particularly, one for reinforcing an automotive vehicle pillar, such as a xe2x80x9cBxe2x80x9d pillar, in an automotive vehicle, such as (without limitation) vehicle roof and pillar structures, door beams and door beam assemblies, frame assemblies, structural rails, rocker panels, and other door striker applications. Generally speaking, these automotive vehicle applications may utilize technology and processes such as those disclosed in U.S. Pat. Nos. 4,922,596, 4,978,562, 5,124,186, and 5,884,960 and commonly owned, co-pending U.S. application Ser. Nos. 09/502,686 filed Feb. 11, 2000 and Ser. No. 09/524,961 filed Mar. 14, 2000, all of which are expressly incorporated by reference. The system generally employs a skeleton member adapted for stiffening the structure to be reinforced and helping to redirect applied loads. In use, the skeleton member is in contact, over at least a portion of its outer surface, with an energy absorbing medium, and particularly heat activated bonding material. In a particular preferred embodiment, the member could be an injection molded nylon carrier, an injection molded polymer, or a molded metal (such as aluminum, magnesium, and titanium, an alloy derived from the metals, and even a metallic foam). Still further, the member adapted for stiffening the structure to be reinforced could comprise a stamped and formed cold-rolled steel, a stamped and formed high strength low alloy steel, a stamped and formed transformation induced plasticity (TRIP) steel, a roll formed cold rolled steel, a roll formed high strength low alloy steel, or a roll formed transformation induced plasticity (TRIP) steel. The chosen member is at least partially coated with a foamable or expandable material, which could comprise an epoxy-based resin, such as L5204, L5206, L5207, L5208 or L5209 structural foam commercially available from L and L Products of Romeo, Mich. Additional foamable or expandable materials that could be utilized in the present invention include other materials which are suitable as bonding mediums and which may be heat activated foams which activate and expand to fill a desired cavity or occupy a desired space or function when exposed to temperatures typically encountered in automotive e-coat and other paint operations. In addition, it is contemplated that the skeleton member could comprise a nylon or other polymeric material as set forth in commonly owned U.S. Pat. No. 6,103,341, expressly incorporated by reference herein.
Though other heat-activated materials are possible, a preferred heat activated material is an expandable or flowable polymeric formulation, and preferably one that is activate to foam, flow or otherwise change states when exposed to the heating operation of a typical automotive assembly painting operation. For example, without limitation, in one embodiment, the polymeric foam is based on ethylene copolymer or terpolymer that may possess an alpha-olefin. As a copolymer or terpolymer, the polymer is composed of two or three different monomers, i.e., small molecules with high chemical reactivity that are capable of linking up with similar molecules. Examples of particularly preferred polymers include ethylene vinyl acetate, EPDM, or a mixture thereof Without limitation, other examples of preferred foam formulation that are commercially available include polymer-based material commercially available from LandL Products, inc. of Romeo, Mich., under the designations as L-2105, L-2100, L-7005 or L-2018, L-7101, L-7102, L-2411, L-2412, L-4141, etc. and may comprise either open or closed cell polymeric base material.
A number of other suitable materials are known in the art and may also be used for vibration reduction. One such foam preferably includes a polymeric base material, such as an ethylene-based polymer which, when compounded with appropriate ingredients (typically a blowing and curing agent), expands and cures in a reliable and predicable manner upon the application of heat or the occurrence of a particular ambient condition. From a chemical standpoint for a thermally activated material, the vibration reducing foam is usually initially processed as a flowable thermoplastic material before curing. It will cross-link upon curing, which makes the material resistant of further flow or change of final shape. For example, in the present invention relating to an automotive pillar, the heat activated expandable material fills a gap between a body side outer panel and a reinforcement panel.
It is also contemplated that foamable or expandable material could be delivered and placed into contact with the skeleton member or vehicle component, such as an automotive pillar, through a variety of delivery systems which include, but are not limited to, a mechanical snap fit assembly, extrusion techniques commonly known in the art as well as a mini-applicator technique as in accordance with the teachings of commonly owned U.S. Pat. No. 5,358,397 (xe2x80x9cApparatus For Extruding Flowable Materialsxe2x80x9d), hereby expressly incorporated by reference. In this non-limiting embodiment, the material or medium is at least partially coated with an active polymer having damping characteristics or other heat activated polymer, (e.g., a formable hot melt adhesive based polymer or an expandable structural foam, examples of which include olefinic polymers, vinyl polymers, thermoplastic rubber-containing polymers, epoxies, urethanes or the like) wherein the foamable or expandable material can be snap-fit onto the chosen surface or substrate; placed into beads or pellets for placement along the chosen substrate or member by means of extrusion; placed along the substrate through the use of baffle technology; a die-cast application according to teachings that are well known in the art; pumpable application systems which could include the use of a baffle and bladder system; and sprayable applications.
In one embodiment the skeleton member along with a suitable amount of bonding or load transfer medium is placed in a cavity defined within an automotive vehicle, such as a vehicle roof structure, pillar structure, door beam assembly, hatch system, or other area or substrate found in an automotive vehicle which could benefit from the structural reinforcement, vibrational reduction, and noise reduction characteristics found in the present invention. In particular, the present invention could be utilized in conjunction with a specific substrate used in many automotive door assembly applications, commonly known in the automotive industry as a door striker. Generally speaking, a door striker is incorporated within a body side of a vehicle and is used in an automotive pillar structure to facilitate the closure and latch of the door in rigid placement suitable for movement of the vehicle. It is contemplated that the bonding medium could be applied to a substrate in a variety of patterns, shapes, and thicknesses to accommodate the particular size, shape, and dimensions of the cavity corresponding to the chosen vehicle application. The bonding medium is activated to accomplish expansion of the resin in the space defined between the skeleton member and the wall structure or body side outer panel defining the cavity. The resulting structure includes the wall structure joined to the skeleton member with the aid of the structural foam.